The present invention relates generally to mining and/or drilling operations. More specifically, the present invention relates to improvements in a chemically-inflatable bag for use in sealing an explosive column.
Typically, boreholes are dug and used as explosive columns. Detonation of a typical, full column confined charge produces a single high amplitude stress wave that crushes the borehole wall and moves out into the surrounding rock producing a crack mechanism. In conjunction with the stress wave, high temperature gases assist in extending the crack formation and moving the rock mass of the ground and sublayers.
By incorporating an air gap (air deck) above, below, or within the explosive column, shock wave reflections within the borehole produce a secondary stress wave. This wave extends the crack formation before gas pressurization. The reduced borehole pressure caused by the air column reduces excessive crushing of the rock adjacent to the borehole wall but still is capable of extending the crack formation and moving the rock out away from the opening of the hole. Air deck volumes of up to about 50% can be used before there is any reduction in fragmentation. By using an air deck, smaller amounts of explosives may be used without much change in fragmentation.
Self-inflating plugs are used to seal boreholes at various depths. A problem with self-inflating plugs currently available is that precise amounts of acid are not used, thus causing variations in performance. In some cases, vinegar is used as the acid, and the concentration of acid in the vinegar is not always consistent. Still another disadvantage with currently available self-inflating plugs is that they are folded such that the folds sometimes prevent them from fully inflating and expanding.
Yet another disadvantage with currently available self-inflating plugs is the way in which the reacting agents are released, causing the self-inflating plugs to inflate. In prior art self-inflating plugs, often an unfurling action is necessary to create a moment of inertia to the bag or other compromising action to the bag is necessary to initiate a reaction between a first reacting agent (powder) and a second reacting agent (liquid). Consequently, a chemical reaction is invoked by introducing the displaced portion of the second reacting agent to the first reacting agent, where a by-product of the chemical reaction is a gas, often CO2. As such, the self-inflating plug expands to an inflated condition by way of the gas being generated by the chemical reaction. It is these such actions that have resulted in difficulties inflating the self-inflating plugs. In other prior art self-inflating plugs, in order to initiate the reaction, it is necessary to break the liquid containing device by stepping or stomping on the self-inflating plug. However, this stepping or stomping action has been known to damage self-inflating plugs.
In order to overcome these disadvantages, an improved self-inflating plug is provided. This self-inflating plug, or chemically-inflatable bag, is able to more easily inflate to fit within a borehole.